Connecting sleeve for a bus bar connection in a gas-insulated switchboard system

ABSTRACT

A connecting sleeve generally used for a bus bar connection is produced from an insulating elastic material, often an elastomer material, having insulating properties which are deteriorated by partial discharges and decrease over the operating time of the switchboard system. According to the invention, so-called partial discharge measuring methods must be carried out, inter alia also in the UHF range (UHF: ultra high frequency), in order to identify damaging effects on the insulating material in time. For the reliable and simple detection of the measuring signals, the connecting sleeve (M) has an outer, electroconductive surface (OA) which is earthed, and an inner, electroconductive surface (OI) to which the voltage potential of the bus bar (S) is applied, in addition to a coupling electrode (KE) which is integrated into the insulating material (I).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a coupling sleeve for a bus barconnection as defined in the preambles of the Patent Claims, as well asto a gas-insulated switchboard system as set out in the preambles of thecorresponding secondary claims, which incorporates such a connectingsleeve.

2. Description of the Related Art

In switchboard systems with gas-insulated switchboard sections or withother modules that are connected to one another through bus barconnections, exacting demands are imposed not only on the electricalcontacts, but also on the gas seals themselves.

Within the area of the bus bar connection, it is customary to use aconnecting sleeve that is of an elastic material, often an elastomer,which is in the form of a tube so as to enclose the bus bar in areliable fashion and insulate it against the environment.

EP-A-1 111 748 describes a bus bar connection that is fitted with suchan insulating connecting sleeve (manchon isolant).

However, the insulating properties can be degraded by partial dischargesand can deteriorate during the operating time of the switchboard system.So-called partial-discharge measurements (TE measurements) must be madein order to ensure safe operation and before the system is put intooperation so as to identify possible damage to the insulating materialand so as to ensure installation that conforms to the relevantstandards. In addition to methods that are base on optical andultrasound principles, a usual method is electrical TE diagnosis(according to IEC 60270), in which the occurrence of partial dischargesis monitored and recorded over time by using measuring sensors, whichare also referred to a coupling electrodes, when the measurement signalsobtained are subjected to intensive signal analysis. The signal analysesare completed in different frequency ranges that extend into the GHzranges, which is to say into the UHF (ultra-high frequency) ranges. Ifsignal analysis is completed in these ultra-high ranges, this is alsoreferred to as UHF-TE diagnosis.

A UHF sensor (UHF coupling electrode) is usually integrated into acast-resin part that is positioned in the gas chamber of the system inorder to record the measurement signals. Or it is provided with avoltage take-off, by way of the bus bar.

These known measures entail the disadvantage that additional componentswith a not inconsiderable space requirement have to be built in, andthis results in additional costs. In addition, in order to wire up thesensors and voltage take-offs, additional seals are needed to route thewiring out of the system. Furthermore, it is only possible to replacethe sensors by entering the system gas chamber, and this makesadditional gas work necessary.

For this reason, it is the objective of the present invention to proposea solution to these problems which permits reliable UFH TE diagnosisthat is both safe and as simple as possible to be performed on a bus barconnection for gas-insulated switchboard systems.

SUMMARY

This objective has been achieved by a connecting sleeve for a bus barconnection having the features set out in the Patent Claims, as well asby a bus bar connection and a gas-insulated switchboard system that isfitted with this, with the features set out in the correspondingsecondary claims.

According to these, it is proposed that the connecting sleeve have anouter, electrically conductive outer surface that is grounded, and aninner, electrically conductive surface to which the voltage potential ofthe bus bar is applied; and in that the connecting sleeve incorporate acoupling electrode that is imbedded in the insulating material.

These measures result in a very reliable measurement system in which thesensor (coupling electrode) is located outside the system gas chamber,so that no gas work is required when the sensor is replaced. Given thisconfiguration of the connecting sleeve and the arrangement of thesensors, the primary capacity of the coupling electrode for the bus baris a function of the surface of the electrode and the distance to theinner conductive layer (the inner, electrically conductive surface). Forthis reason, the primary capacity can be very large without thisaffecting the dielectric strength of the sleeve. It is thus possible toachieve a high partial-discharge sensitivity of the sensor (couplingelectrode).

Particularly advantageous configurations of the present invention areset out in the secondary claims.

According to these, it is particularly advantageous that the couplingelectrode have a sensor surface that is tangential to the outer surface.This makes it possible to avoid a field increase occurring in the areaof the electrode, since this would affect the UHF TE measurement.

In this connection, it is advantageous that the coupling electrode be soimbedded in the insulating material that the coupling electrode isinsulated from the inner surface and from the outer surface, and thatthe coupling electrode have an edge area that is lined up so that itoverlaps the outer surface, at least in part.

It is also a particular advantage if the coupling electrode is connectedwith a plug-type connector that is located in an opening that issurrounded by the insulating material. In this connection, it is alsoadvantageous if the plug-type connector can be connected with a matingelement; and that the opening be matched to the outside shape of thismating element to form a dust- and moisture-proof plug connection. Thesemeasures create a reliable connection possibility for measuringequipment, in particular for voltmeters and spectrum analyzers.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described in greater detail below on thebasis of one embodiment shown in the drawings appended hereto. Thesedrawings show the following:

FIG. 1: The bus bar connection with a connecting sleeve according to thepresent invention, in cross section;

FIG. 2: The connecting sleeve according to the present invention, in adifferent cross section.

FIG. 1 is a cross section through a bus bar connection SK that isintended to connect two switchboard sections F1, F2 (left-hand andright-hand parts of the drawing, respectively).

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE PRESENT INVENTION

There are bus bar tubes S in the gas containers of the two switchboardsections F1 and F2; one end of each of these extends from the gascontainer so that they can be connected to one another through the busbar connection SK. To this end, the bus bar tubes S are coaxial to eachother, and the ends of each of them extend from an opening that issealed off by sealing rings (O-rings). All of the leadthroughs arelocated on a container support and are sealed by O-rings so as toprevent the egress of insulating gas. One bus bar tube S of the secondswitchboard section F2 (right-hand part of the drawing) extends furtherout of its opening than the corresponding part of the first bus bar tube(left-hand part of the drawing).

A connecting sleeve M extends around the bus bar ends (ends of the busbar tubes S), and this is in the form of a tube and of an elasticinsulating material I, preferably an elastomer. The sleeve M is securedto the outer wall of the switchboard sections F1 and F2 through flangesFL and encloses the parts of the bus bar that extend beyond theswitchboard sections. The connection is electrically insulated from andprotected against the environment by this sleeve M.

According to the present invention, the sleeve M has an inner conductivesurface OI that is in electrical contact with the bus bar S so that itsvoltage potential is applied to this inner surface OI. In addition, thesleeve M has an outer surface OA that is also electrically conductive.This outside surface OA is grounded through the flange and the walls ofthe gas containers of the switchboard sections F1 and F2.

A sensor in the form of a coupling electrode KE is incorporated in themiddle area of the connecting sleeve M In order to capture themeasurement signals during TE UHF measurement. The coupling electrode KEis positioned in the insulating material I and is formed as a concavecurved surface that is tangential to the outer surface OA. The couplingelectrode can be of a conductive material or of a semiconductor plastic.A contact pin is attached to the coupling electrode KE, and this pinforms part of a plug-type connector that is positioned in an opening andso can be connected to measuring equipment through a matching plug(counterpart of the connection).

FIG. 2 is another cross sectional view of the sleeve M and shows thecoupling electrode that is integrated therein more precisely.

As can be seen, the coupling electrode KE itself is imbedded in theinsulating material I, with the edge area R of the sensor surface of thesensor surface overlapping the outside surface OA of the sleeve M. Theelectrode KE is thus separated from the grounded outside surface OA by athin layer of insulating material I. Because of this, and because of thetangential orientation of the sensor surface, there is no noteworthyincrease of the field in the area of the electrode. This entails theadvantage that the primary capacity of the coupling electrode for thebus bar S is a function of the sensor surface of the electrode KE andthe distance to the inside surface OI. For this reason, the primarycapacity can be very large without affecting the dielectric strength ofthe sleeve M. Because of this, it is possible to achieve greatsensitivity of the sensor KE to partial discharge.

Contact with the sensor KE is made through the plug-type contact S1 thatis positioned within an opening A in the sleeve M and thus forms asocket in which the plug S2 fits exactly and is dust- and water-proof.Since the sensor KE is accessible from outside and is also locatedoutside the gas chamber, not only is it very simple to establish ameasurement contact; it is also possible to effect any replacement ofthe sensor KE that may become necessary without any difficulty.

The system as a whole contains only a few inexpensive components. Noadditional seals of the like are required, and there is no requirementfor additional space.

For this reason, the system that is proposed is well suited for use ingas-insulated switchboard systems. Other potential applications arepossible, such as its use in power transformers and the like.

1. Connecting sleeve for a bus bar connection, having inner and outerelectrically conductive surfaces, that is used to connect twoswitchboard sections of a gas-insulated switchboard system, wherein: theconnecting sleeve is an insulating, elastic material that is in the formof a tube; the outer, electrically conductive surface of the connectingsleeve is grounded; the connecting sleeve has a sensor in the form of acoupling electrode that is imbedded in the insulating material andelectrically insulated from the inner and outer electrically conductivesurfaces of the connecting sleeve; and the connecting sleeve has ahollow center which encompasses the bus bar connection, and wherein thevoltage potential of the bus bar is applicable to the inner,electrically conductive surface of the connecting sleeve.
 2. Connectingsleeve as defined in claim 1, wherein the sensor has a sensor surfacethat is tangential to the outer surface.
 3. Connecting sleeve as definedin claim 1, wherein the sensor has an edge area that overlaps the outersurface, at least in part.
 4. Connecting sleeve as defined in claim 1,wherein the sensor is connected to a plug connector that is positionedin an opening that is surrounded by the insulating material. 5.Connecting sleeve as defined in claim 4, wherein the plug connector canbe connected to a mating element; and in that the opening is matched tothe outer shape of this mating element so as to form a dust-proofplug-type connection.
 6. Gas-insulated medium-voltage switchboardsystem, with at least two switchboard sections that are connected to oneanother through a bus bar connection that incorporates the connectingsleeve of claim 1.